Fogging, icing and misting may form on vehicle glass under certain environmental conditions. For example, ice may form on the exterior surface of vehicle glass when ambient temperature is below freezing. In addition, condensation may form on the inside surface of the glass when there is high relative humidity inside the vehicle and where the glass is cool due to a lower temperature outside the vehicle. Condensation may also form on the outside of the glass if cold air is blown onto the inside of the glass in an attempt to remediate a misting condition.
Existing vehicles may have a heating, ventilation and air-conditioning (HVAC) system that provides an airflow for clearing precipitation from the vehicle glass, preventing fog or ice from forming on the glass or providing a desired air temperature within the passenger cabin. To that end, the HVAC system may include a climate control head unit having controls that allow a user to operate the HVAC system by, for example, selecting a desired temperature. The HVAC system may further include a controller coupled to the climate control head unit to facilitate the configuration of additional settings, such as fan speed, air conditioning (A/C) compressor operation, and recirculation. Based on these settings, the controller may control a blower and the positioning of various air doors, in order to provide a flow of recirculated air or fresh air through an evaporator core or a heater core. In addition, existing HVAC systems may also have ductwork packaged in a vehicle in a way that may reduce or even prevent effective airflow along the perimeter of the vehicle glass, which may decrease the effectiveness of airflow-based defrosting or clearing of the glass along those portions. Furthermore, the airflow may be limited by other constraints, including vehicle styling, electronics packaging or features accessible to vehicle occupants, including a heads up display (HUD).
The HVAC system may further have an electronic automatic temperature control (EATC) module configured to automatically defrost the vehicle glass or adjust the level of heating and cooling in the vehicle, based on status signals received from sensors and controllers located throughout the vehicle. However, existing EATC modules and manual user inputs may have issues with the efficiency or effectiveness in keeping the windshield and other vehicle glass sufficiently clear.